1. Field of the Invention
The present invention relates to an optical apparatus using reflection, refraction, or diffraction, and more specifically, to an optical apparatus for providing an image with a deep depth of field to a user and having a wide available range of an optical module included in the optical apparatus.
2. Description of the Related Art
An augmented reality (AR) is a technology for enabling a user to see a virtual screen (virtual world) superimposing a real world which the user sees with eyes. The AR has been called a mixed reality in the early stage because a single image is displayed by combining the real world with the virtual world having additional information in real time.
The AR has begun to be studied starting with the development of a see-through head mounted display (HMD), the AR has a meaning different from a virtual reality (VR). Whereas the user cannot see the actual environment because the VR leads the user to be immersed in a virtual environment, the AR allows the user to see the actual environment, and has the form of mixing the actual environment with a virtual object. In other words, there is a difference in that the VR shows the virtual world to the user by replacing the real world, however, the AR shows the real world to the user by supplementing the real world by superimposing the virtual object on the real world.
In order to realize the above AR, the HMD is mainly used, however, a lens module (an optical system module) of the HMD has a problem in that it is very difficult to manufacture due to its complicated structure, and the lens module has a large size and heavy weight due to the complicated structure.
As one of apparatuses for implementing the conventional augmented reality, ‘Patent Document 1 (KR 10-1646873 B1)’ discloses a head mounted display device having a rotational hinge structure in a goggle module. The head mounted display device having a rotational hinge structure in a goggle module of Patent Document 1 has a technical feature of having a hinge structure to view the virtual screen only by moving eyeballs up and down while fully securing the external view.
Patent Document 2 (KR 10-1524933 B1) discloses an optical system and a head mounted display apparatus for augmented reality implementation. The optical system and the head mounted display apparatus for the augmented reality implementation include: a first reflective unit for transmitting a first image which is a part of the real image and changing an optical path of a second image which is a remaining part so as to minimize the deviation when a virtual image (virtual screen) is matched with a real image (external view); a second reflective unit for re-changing the optical path of the second image; an image collection unit for collecting the second image; a controlling unit for generating the virtual image based on the second image, and enabling the virtual image to be outputted from a display panel; an enlarging lens unit for enlarging the virtual image outputted from the display panel; and a third reflective unit for enabling the virtual image enlarged through the enlarging lens unit to be imaged on a retina of a user.
Due to the above structural problems, the conventional apparatus for implementing the augmented reality including ‘Patent Document 1’ and ‘Patent Document 2’ has a problem that the number of lens modules, the arrangement form of the lens module, and the arrangement form of the display module (device) are very limited.
In addition to the above problem, there is a problem in that the conventional lens module fails to provide the user with a constantly clear virtual screen although the conventional apparatus for implementing the augmented reality has a complicated structure.
As described above, the AR is the technology for superimposing the virtual screen so as to enable the user to simultaneously recognize the virtual screen when the user recognizes the real world. When the user recognizes (looks at) the real world, if the user focuses on where the user wants by focusing on a far or near distance (if the user changes a focal distance), the virtual screen may look blurry or clear. In other words, because the focus of the lens module for providing (reflecting) the virtual screen is fixed, the user may see the clear virtual screen only when the focus is in while changing the focal distance, however, the user sees the blurred (unclear) virtual screen when it is out of focus.
As one of conventional arts to solve the above problems, Patent Document 3 (KR 10-2015-0116142) discloses a focus-adjustable optical system module for a head mounted display. More specifically, the focus-adjustable optical system module for a head mounted display of Patent Document 3 includes: a screen transfer lens for receiving a virtual screen from a display panel, total-internal-reflecting the received virtual screen, and transferring the virtual screen to a next optical system; an adjusting prism for receiving the virtual screen transferred from the screen transfer lens, and adjusting the focus through reflecting the virtual screen by adjusting an angle so as to transfer the virtual screen to the next optical system; and a combiner for reflecting the virtual screen transferred from the adjusting prism and combining the real screen from the outside so as to transfer the combined screen to wearer's eyes.
The focus-adjustable optical system module for the HMD of Patent Document 3 is capable of a focus adjustment. However, the focus adjustment refers to that the user adjusts the focus and focuses on (fixes) one of views at which the user mainly looks, and it totally fails to solve the problem pointed out above in that the user obtains the unclear virtual screen when changing the focal distance while gazing at the real world.
In addition, as one of conventional arts to solve the above problems, Patent Document 4 (KR 10-2013-0126623 A) discloses an augmented reality system and a method of providing an improved focus. More specifically, the augmented reality system and the method of providing the improved focus of Patent Document 4 include: a processor for determining a current user focus area under control of software; and a focus area adjustment unit for focusing a variable focus lens within the current user focus area under control of the processor. The augmented reality system and the method of providing the improved focus of Patent Document 4 totally fail to solve the above problems in view of a physical scheme. Because an additional processor is required to determine the current user focus area and additional software is required to control the processor, the software and processor may have malfunctions and errors. Further, the manufacturing cost is high due to the additional installation of the processor and software.